While many of the devastating effects of the Acquired Immune Deficiency Syndrome (AIDS) appear to result from the infection of CD4+ lymphocytes, it is clear that human immunodeficiency virus (HIV), the causative agent, can also infect monocytes and macrophages. Infection of monocytic cells may be important int he initiation and propagation of persistent, low-level infection; in AIDS encephalopathy; in the release of inflammatory mediators, like tumor necrosis factor and interleukin 1 (IL-1); in suppression of hematopoiesis, and in the immune defects seen in AIDS. The objective of this proposal is to develop vectors which are capable of blocking HIV expression in monocytic cells, using cell-type specific promoters driving the expression of anti-HIV constructs. The specific aims are: (1) To study the effects of HIV infection of monocytic cells, particularly with respect to the effects on expression of monocytic cell surface markers and differentiation of these cells. We shall measure the expression of CD14, CD18, and other monocytic markers in myeloid cell lines, in monocytes and macrophages, and in bone marrow myeloid cells susceptible to different isolates of HIV-1 and HIV-2; and investigate the effects of differentiating agents like phorbol esters and cytokines on the expression of these markers in HIV infected versus uninfected cells. (2) To characterize in detail the promoters and regulatory elements of monocyte specific genes, particularly CD14 and CD18, and to isolate those elements of the promoters which are capable of driving the expression of heterologous genes in monocytes and macrophages. (3) To use these characterized promoters to develop vectors encoding of blocking the expression of specific HIV gene products essential for HIV viral replication in monocytic lines. (4) To develop vectors containing these monocytic promoter/anti-HIV constructs which can be efficiently introduced into bone marrow cells and block HIV infection of these cells. These studies should provide a focused but comprehensive approach to development of a model of gene therapy for AIDS.